Protector for high temperature furnace insulation supports

ABSTRACT

An insulating construction system for high temperature applications comprising a structural supporting member in refractory insulating bodies arranged to protect the supporting member at the points where it is exposed to high temperatures. The refractory insulating body acts to increase the useful life of the supporting member and allows greater latitude in the choice of materials for the member, resulting in greater ease of construction and increased efficiency of operation during the use of the member in high temperature applications.

United States Patent [1 1 Byrd, Jr.

[ PROTECTOR FOR HIGH TEMPERATURE FURNACE INSULATION SUPPORTS [75] Inventor: Carlisle 0. Byrd, Jr., Houston, Tex.

[73] Assignee: The Carborundum Company,

Niagara Falls, NY. [22] Filed: Aug. 23, 1971 [21] Appl. No.: 173,939

[52] US. Cl 52/506, 52/410, llO/l A [51] Int. Cl. F23m 5/00, E04b 1/62 [58] Field of Search t. 52/410, 506, 378,

52/700, 701, 249, 712; llO/l, l A, 1 B

[56] References Cited UNITED STATES PATENTS 2/1944 Hensel 110/1 B OTHER PUBLICATIONS Dictionary of Ceramics by Dodd 1967 by George [451 July 3,1973

Newnes Limited.

Primary Examiner-John E. Murtagh Attorney-David E. Dougherty et al.

[57] ABSTRACT An insulating construction system for high temperature applications comprising a structural supporting member in refractory insulating bodies arranged to protect the supporting member at the points where it is exposed to high temperatures. The refractory insulating body acts to increase the useful life of the supporting member and allows greater latitude in the choice of materials for the member, resulting in greater ease of construction and increased efficiency of operation during the use of the member in high temperature applications.

11 Claims, 7 Drawing Figures PATENTEUJULS ma INVENTOR.

CARLISIE O. BYRD JR. BY flaw a wall PROTECTOR FOR HIGH TEMPERATURE FURNACE INSULATION SUPPORTS BACKGROUND OF THE INVENTION and supporting composite walls, ceilings or panels,

comprising thermal insulations of assorted insulating compositions resistant to very high temperatures up to a range of about 2500 to 3000F and suitable for direct exposure to the source of heat as in enclosing structures for furnaces, soaking pits, annealing furnaces, thermal stress, relief chambers and likehigh temperature equipment. The invention is particularly concerned with practical and effective means of uniting and securing non or weak structural insulations, such as bodies of refractory fiber, and of high thermal tolerances with structural or supporting members such as steel or other appropriate metal plates or sheets, and so forth, to provide composite sections of integrated insulation and supporting or carrying structure, providing complete units suitable by themselves for use as walls, ceilings or panel components for furnaces and the like foregoing high temperature chambers.

Conventional high temperature installations such as furnaces, soaking pits, stress relieving units, annealing furnaces, and so forth, are constructed with walls and- /or tops of refractory brick or block, such as insulating firebrick, normally braced or even supported with metal structures, and of compositions which typically range in densities of from about 25 lbs/cu ft for maximum exposure temperatures of approximately 1600F up to about 65 lbs/cu ft for a maximum exposure temperature of approximately 3000F. Of paramount significance in the use of such conventional construction means and material is the high cost of installation comprising a relatively slow assembly of the structure with brick or like block units with refractory mortar and the requirement therefor of skilled masons. Moreover, these brick type constructions, aside from high initial construction cost and high weight, are by nature quite rigid, and, therefore, prone to cracking and breakage, or spalling and so forth, due to thermal expansion, present extensive joint exposure, and are costly to repair, among other significant disadvantages.

The use of dense refractories, such as bricks or block structures, is often required in high temperature equipment where the refractory is subjected to abrasion or comes in contact with fused materials, such as molten glasses or metals. Many applications, however, are for furnace interiors in which only hot gases are in contact with the refractory liner, in these cases lining materials of lower density and mechanical strength are suitable and have the advantages of reduced weight and greater ease of installation. The invention therefor comprises a construction method for the installation of this type of furnace lining system and, more specifically, a fastening method for the attachment of the linings to furnace walls and roofs. In previous designs, the fastening devices sometimes fail prematurely because of inadequate protection against high temperatures. This causes extensive furnace downtime for repairs. The invention therefor provides means for protecting the insulation fastening devices, these means being easily installed and retaining their effectiveness for extended periods of furnace operation.

SUMMARY OF THE INVENTION This invention comprises a high temperature insulation construction for direct exposure to high temperature environments comprising a structural supporting member, a body of insulating material superimposed over the structural supporting member, said body of insulating material being secured to the structural supporting member by means of a plurality of spaced apart studs of metallic composition passing through the body of insulating material with the first end of the stud secured to the structural supporting member and the second end extending through and protruding from the surface of the body of insulating material, the stud having shoulder means for holding the body of insulating material and, a refractory protector applied around said shoulder means and stud end for protection during exposure to high temperatures.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a portion of a furnace wall and lining, showing one method of fastening the lining.

FIG. 2 is an end view of the fastening nut, washer and refractory protector.

FIG. 3 is a sectional view similar to that of FIG. 1, showing an alternate type of fastener protector.

FIG. 4 is a view of the contact surface of the refractory protector of FIG. 3.

FIG. 5 is a sectional view similar to that of FIG. 1, showing a second modification of the lining fastener.

FIG. 6 shows the washer fastener as used in FIG. 5.

FIG. 7 shows a third modification of the lining fastener stud.

DESCRIPTION OF THE PREFERRED EMBODIMENT A portion of a furnace wall, having an insulating lining and lining fastener, is shown in FIG. I. The furnace shell 10 has a stud l2 fastened to it by welding or other suitable means. The stud projects into the furnace interior and is made long enough to penetrate the layer of insulating lining 20, 22 and permit the attachment of the appropriate fastening means. The end of the stud is threaded to cooperatively engage with the threads of a holding nut 16. This holding nut is tightened against a large washer 18. The stud 12, holding nut 16 and washer 18 may be made of carbon or alloy steel, depending on the degree of temperature at which the furnace will operate. Special alloy steels are more resistant to high temperatures but are expensive. Even the most resistant alloys tend to weaken during extended service. When they fail, the lining loses its support and comes loose, hot furnace gases may then penetrate to the furnace shell, causing decreased furnace efficiency and weakening the shell. The effects are even worse if a furnace roof lining fails, since much of the heat is concentrated in this area. Some means of protecting the hot end of the stud I2 is highly desirable, and this is provided by the refractory protector 24. This is a cup-like refractory shape which may be formed by pressing or vacuum casting a composition comprising suitable refractory fibers such as aluminum silicate with appropriate binders and firing the resulting shape to give a strong refractory protector body 24. A hole is formed in the center of the refractory protector 24 which allows it to fit upon stud 12, followed by the metal washer 18 and holding nut 16. The refractory protector 24 is of sufficient strength to transfer the compressing force of holding nut 16 to the lining materials 20 and 22 and insure their firm support. For purposes of illustration the lining shown in FIG. 1 comprises a layer of mineral wool 20, covered by a layer comprising aluminum silicate fibers 22. The lining fastener assemblies of the invention are not limited to these specific types of fibers, however, but may be employed with any type of fibrous heat resistant material, either fabricated as felts or blankets, or in more rigid compositions such as insulating boards, panels or blocks.

An end view of the refractory protector 24, washer 18 and holding nut 16 is shown in FIG. 2. After this assembly has been made and the holding nut tightened properly, the refractory protector cap is filled with a cast or refractory mixture 28 sufficient to completely fill the cap and cover the washer 18, holding nut 16 and the end of the stud 12. If the stud protrudes too far, it is cut off before the refractory mixture is applied. Any suitable castable refractory may be used, provided its coefficient of expansion is such that it will not rupture the protector body 24 when the assembly is brought up to furnace temperature. Since these temperatures may range up to about 2500F to 3000F, the refractory protector cup and castable refractory mixture must be stable to the upper limit of this temperature range.

An alternate means for stud fastener protection is shown in FIG. 3. This consists of a cap 30 molded or otherwise formed from an appropriate refractory comprising fibers such as aluminum silicate or similar heat resistant fibers or filaments and suitable filler or binder's. Molded or otherwise secured within the cap 30 is a holding nut 32. This may be either a threaded nut or a similar threaded member suitable for firm attachment within the cap 30, the threads of the nut or member cooperating with threads 14 on stud 12. The cap 30 contains an internal cavity 34 to give clearance space for the end of stud 12 when the cap 30 is tightened against insulation body 22. A protruding rim 36 is formed adjacent to the outer periphery of cap 30, this functions as a sealing aid. The inner surface of cap 30 is shown in FIG. 4, showing the hexagonal shape given to the periphery 38 of the cap to facilitate the tightening operation. This type of holding device has the advantage of rapid installation with the elimination of the step where castable refractory mix is required for filling in the refractory protector and covering the holding nut and washer. Installation is facilitated, especially for work in confined places or for furnace roof installations where the use of castable mix is difficult.

A modification of the fastening stud is shown in'FIG. in which the stud is not threaded but has one or more radial slots 42 cut near its outer extremity. The retaining washer 44 has a center keyhole opening 46 (see FIG. 6) which permits washer 44 to fit over the end of stud 12 and snap into one of the radial slots 42, thus holding the refractory protector 24 and the lining insulation and 22 in place. The protruding end of stud 12 is then cut off and the exposed stud end and the washer 44 is then covered by a second refractory protector 48. Both refractory protectors 24 and 48 are made from the same type of refractory composition, the protector 48 being shaped for a force fit when inserted within the inner periphery of refractory protector 24.

In FIG. 7, an alternate form of stud construction is shown, in which the stud has several holes 52 drilled or otherwise formed near the end of the stud. The refractory protector 24 and washer 44 are assembled as.

shown in FIG. 5 and are held in place against the furnace liner by insertion of a cotter pin 54 in one of the stud holes. The protruding end of stud 12 is then cut off and the second refractory protector 48 attached as shown in FIG. 5.

The fastening methods as provided by this invention provide a means of protecting the metal parts of the fastening system against high furnace temperatures, thereby prolonging a useful life of the fasteners and permitting extended furnace operation. The refractory protectors used increase the area of support from each stud so that fewer studs are needed. Furnace heat losses are reduced since there is less heat transfer through the metal studs to the furnace walls. In many applications, the refractory protectors of the invention will permit the use of less expensive fastening materials, thus reducing the cost of furnace construction and maintenance during operation.

What is claimed is:

1. A high temperature insulation construction for direct exposure to high temperature environments comprising: (a) a structural supporting member, (b) a body of insulating material superimposed over the structural supporting member, (0) said body of insulating material being secured to the structural supporting member by means of a plurality of spaced apart studs of metallic composition passing through the body of insulating material with the first end of the stud secured to the structural supporting member and the second end extending through and protruding from the surface of the body of insulating material, the studs having fastening means for holding the body of insulating material, and (d) a separate refractory protector comprising a cup-like fired refractory shape formed to encircle the second end of the stud and partially enclose the fastening means.

2. A high temperature insulation construction according to claim 1, in which the said fastening means comprises a metallic washer and holding nut, said nut engaging cooperating threads formed on the second end of said stud.

3. A high temperature insulation construction according to claim 1, in which the said fastening means comprises a ceramic cap with a threaded metalic insert firmly bonded therein, said threaded insert engaging cooperating threads formed on the second end of said stud, whereby the said fastening means is protected by the said ceramic cap.

4. A high temperature insulation construction according to claim 1, in which the said fastening means comprises a metallic washer having a central opening, said washer engaging cooperating grooves formed on the second end of said stud, and a refractory protector applied around said fastening means for protection during exposure to high temperature.

5. A high temperature insulation construction according to claim 1, in which said refractory shape is filled with a castable refractory composition which completely covers and protects the said fastening means.

6. A high temperature insulation construction according to claim 1, in which said refractory shape is second refractory disc, said second disc covering said shoulder means for protection during exposure to high temperature.

10. A high temperature insulating construction according to claim 4, in which the second end of said stud has at least one radial hole formed therein, said stud acting in conjunction with a cotter pin inserted in the hole to hold the metallic washer and refractory protector in position on the said fastening means.

11. A high temperature insulation construction according to claim 9, in which both refractory members are formed from a mixture comprising aluminum silicate fibers. 

1. A high temperature insulation construction for direct exposure to high temperature environments comprising: (a) a structural supporting member, (b) a body of insulating material superimposed over the structural supporting member, (c) said body of insulating material being secured to the structural supporting member by means of a plurality of spaced apart studs of metallic composition passing through the body of insulating material with the first end of the stud secured to the structural supporting member and the second end extending through and protruding from the surface of the body of insulating material, the studs having fastening means for holding the body of insulating material, and (d) a separate refractory protector comprising a cup-like fired refractory shape formed to encircle the second end of the stud and partially enclose the fastening means.
 2. A high temperature insulation construction according to claim 1, in which the said fastening means comprises a metallic washer and holding nut, said nut engaging cooperating threads formed on the second end of said stud.
 3. A high temperature insulation construction according to claim 1, in which the said fastening means comprises a ceramic cap with a threaded metalic insert firmly bonded therein, said threaded insert engaging cooperating threads formed on the second end of said stud, whereby the said fastening means is protected by the said ceramic cap.
 4. A high temperature insulation construction according to claim 1, in which the said fastening means comprises a metallic washer having a central opening, said washer engaging cooperating grooves formed on the second end of said stud, and a refractory protector applied around said fastening means for protection during exposure to high temperature.
 5. A high temperature insulation construction according to claim 1, in which said refractory shape is filled with a castable refractory composition which completely covers and protects the said fastening means.
 6. A high temperature insulation construction according to claim 1, in which said refractory shape is formed from a fired mixture comprising aluminum silicate fibers.
 7. A high temperature insulation construction according to claim 3, in which the ceramic cap is formed from a castable refractory.
 8. A high temperature insulation construction according to claim 3, in which the castable refractory is formed from a mixture comprising aluminum silicate fibers.
 9. A high temperature insulation construction according to claim 4, in which the refractory protector comprises a cup-like refractory member shaped to fit on said stud beneath the said fastening means, said protector having a flanged rim for frictionally engaging a second refractory disc, said second disc covering said shoulder means for protection during exposure to high temperature.
 10. A high temperature insulating construction according to claim 4, in which the second end of said stud has at least one radial hole formed therein, said stud acting in conjunction with a cotter pin inserted in the hole to hold the metallic washer and refractory protector in position on the said fastening means.
 11. A high temperature insulation construction according to claim 9, in which both refractory members are formed from a mixture comprising aluminum silicate fibers. 